<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>ul tree组件</title>
    <script defer src="ExpandableList.js"></script>
</head>
<body>
<div>
    <ul is="expandable-list" data-expanded>
        <li>a</li>
        <li>b</li>
        <ul is="expandable-list" data-expanded>
            <li>a</li>
            <li>b</li>
        </ul>
    </ul>
</div>
</body>
</html>